CVE-2019-18277
In legacy mode, messages featuring a transfer-encoding header missing the "chunked" value were not being correctly rejected.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 10.1%, higher than 96% of all known CVEs. Patch or mitigate before the next change window.
Description
A flaw was found in HAProxy before 2.0.6. In legacy mode, messages featuring a transfer-encoding header missing the "chunked" value were not being correctly rejected. The impact was limited but if combined with the "http-reuse always" setting, it could be used to help construct an HTTP request smuggling attack against a vulnerable component employing a lenient parser that would ignore the content-length header as soon as it saw a transfer-encoding one (even if not entirely valid according to the specification).
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- EPSS
- 10.07% probability · 96th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-444
- Affected
- haproxy/haproxy
- Source
- cve@mitre.org
EPSS 10.1% since 3 November 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00016.html
- http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00019.html
- https://git.haproxy.org/?p=haproxy-2.0.git%3Ba=commit%3Bh=196a7df44d8129d1adc795da020b722614d6a581
- https://lists.debian.org/debian-lts-announce/2022/05/msg00045.html
- https://nathandavison.com/blog/haproxy-http-request-smugglingExploit, Third Party Advisory
- https://usn.ubuntu.com/4174-1/
- https://www.mail-archive.com/haproxy%40formilux.org/msg34926.html
- http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00016.html
- http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00019.html
- https://git.haproxy.org/?p=haproxy-2.0.git%3Ba=commit%3Bh=196a7df44d8129d1adc795da020b722614d6a581
- https://lists.debian.org/debian-lts-announce/2022/05/msg00045.html
- https://nathandavison.com/blog/haproxy-http-request-smugglingExploit, Third Party Advisory
- https://usn.ubuntu.com/4174-1/
- https://www.mail-archive.com/haproxy%40formilux.org/msg34926.html
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.